A necklace is an article of jewelry which is worn around the neck. Necklaces are frequently formed from a metal jewelry chain, often attached to a locket or pendant. Necklaces can also be manufactured with cloth, and they sometimes contain rocks (particularly gems), wood, and/or shells with different shapes and sizes. Necklaces have been an integral part of jewelry since the time of ancient civilizations. The birth of necklaces is believed to be as old as the Stone Age, which is around 40,000 years old. At that time, people were decorating themselves with mollusk necklaces. Later, necklaces made of stones, bones, shells and animal teeth became popular. After the discovery of metals, gold, silver and a variety of other metals were used to make eye-catching necklaces for both men and women.